Coinrail said hackers stole cryptocurrencies over the weekend including Pundi X, Aston and NPER. It did not give a value but Yonhap News agency cited unnamed industry sources saying coins worth about 40 billion won ($37 million) were lost.

If true, that would make it the biggest cryptocurrency theft reported to date in South Korea.

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Bitcoin was trading at US$6,780 on Monday, down from more than $7,500 before the weekend, according to Coindesk, which monitors prices.

Coinrail said it was co-operating with police and suspended trading. News reports said Coinrail, launched in September, was the seventh-largest exchange in South Korea by trading volume.

South Korea has seen a craze over bitcoin and other cryptocurrencies, prompting authorities to try to rein in speculative investment this year by tightening regulations. Cryptocurrencies still are popular, especially with young investors.